1. Field
The invention generally relates to an implant method and an implanter for implanting substrate, and more particularly relates to a method and an implanter capable of implanting different portions of one or more substrate by using different customized ion beams shaped respectively by a variable aperture located right in front of the one or more substrate.
2. Description of Related Art
In general, as shown in FIG. 1A, an implanter has at least an ion source 101 and an analysis magnet 102. An ion beam 103 is generated by the ion source 101 and then analyzed by the analysis magnet 102 to screen out the ions with un-desired charge-mass ratio(s). After that, the ion beam 103 is implanted into a substrate 104 (such as a wafer or a panel). As usual, the quality of the ion beam 103 outputted from the analysis magnet 102 is not good enough for efficiently implanting the substrate 104. For example, the ion beam current distribution on the cross section of the ion beam 103 may be undulant or have a long tail. Then, the implantation of the ion beam 103 on the substrate 104 may be non-uniform if no extra step/device is used to improve the distribution of implanted ions (or atoms and/or molecules) in the substrate 104. For example, it is common that in certain beam current and/or energy range for a given species of ion beam 103, the beam shape, size or cross section falls short from the spec requirements. Then, the dose distribution control for one or more dose regions on the substrate 104 cannot be optimized. For example, for dose split or other non-uniform implantation, different portions of the substrate 104 require different doses. Then, even the quality of a fixed ion beam 103 is well qualified for one dose region, different portions still have to be implanted differently for providing different doses by using the fixed ion beam 103. Note that this is true for both types of beams typically used, the spot ion beam and the ribbon ion beam.
One prior art, as shown in FIG. 1B, improves these disadvantages by using the magnet assembly 105 to further enhance the beam optics for modifying (deforming, collimating and/or deflecting) the beam 103 in a position between the analysis magnet 102 and the substrate 104. As usual, the magnet assembly 105 has one or more magnet, where each magnet may provide a uniform or non-uniform magnetic field. However, the details of the magnet assembly 105 are not limited. Herein, as an example, the magnet assembly 105 is located around the trajectory of the ion beam 103, such that the motion of each ion of the ion beam 103 is directly modified by the magnetic field generated by the magnet assembly 105. Hence, by properly adjusting the operation of the magnet assembly 105, such as adjusting the current applied to the magnets or adjusting the relative geometric relations among different magnets, the ion beam 103 is correspondingly modified and then the projected area of the ion beam 103 on the substrate 104 can be correspondingly adjusted. However, the cost of the magnet assembly 105 is high, the precise adjustment of the magnetic field is difficult, and the process of modifying ion beam by the magnetic field is complex and time consuming.
Another prior art, not shown in any figure, improves these disadvantages by adjusting the operation of the ion source 101 and/or the analysis magnet 102, such that the ion beam 103 outputted from the analysis magnet 102 may be modified well. However, the cost is high and the operation is complex, and the room for adjustment of the ion beam 103 is limited. The other prior art, not shown in any figure, improves these disadvantages by adjusting the scan parameter(s), such as scan path pitch and the scan speed, such that different implantation are differently achieved by the same ion beam 103. Similar, the cost and the operation still is high and complex, and the room for adjustment of the scan parameter(s) is limited.
Still one prior art, as shown in FIG. 1C, improves these disadvantages by using an aperture device 106 with a fixed aperture 107 to shape the ion beam 103 before the substrate 104 in implanted by the shaped ion beam 103. Reasonably, by properly choosing the fixed aperture 107, the ion beam 103 can be shaped without modifying the ion beam 103 itself. In other words, the prior art does not need to further modify the ion beam 103 outputted from the analysis magnet 102 by any magnetic/electric filed and also does not need to adjust the operation of the ion source 101 and/or the analysis magnet 102. In addition, the fixed aperture only can shape the ion beam 103 but cannot adjust the ion beam 103, such as adjusting the ion beam current distribution on the cross section of the ion beam 103. Hence, another prior art as shown in FIG. 1D positions the fixed aperture 107 within the aperture device 106 at an end of a beam optics and right in front of the substrate 104. Hence, after the ion beam 103 is modified by the beam optics, the ion beam 103 can be further shaped by the fixed aperture 107 again to achieve better shape of projected area of the ion beam 103 on the substrate 102. In other words, by using the fixed aperture 107, the required adjustment of the ion beam 103 provided by the beam optics can be less strict than the required adjustment of the ion beam provided by the beam optics without using any aperture. However, the two prior arts have a major disadvantage: lack of flexibility. The shape and the size of a fixed aperture 107 is fixed, and then the room for adjusting of the shaped ion beam 103 is finite even the overlap between the ion beam 103 and the fixed aperture 107 is changed by shifting the aperture device 106 aperture device along a direction vertical to the ion beam 103 and/or rotating the aperture device 106 around another direction in three-dimensional space at intersecting of the ion beam 103 through a tilt or twist mechanism. Hence, multiple aperture devices 106 with different fixed apertures 107 are required and then the implantation on one or more substrate 104 may be interrupted several times for substituting the multiple aperture devices 106 to use different fixed apertures 107 for achieving different implantations.
Accordingly, it is still desirable to develop different approach to improve the above disadvantages, especially to develop a simple and cheap approach.